A well-known vehicle includes a fastening resin structure such as a dash panel or front pillar made from carbon fiber reinforced plastic (CFRP), and a front side member of aluminum alloy attached to the fastening resin structure by means of a bolt and a nut, as disclosed in JP-A-2007-290426.
The fastening resin structure disclosed in JP-A-2007-290426 includes a resin member, i.e., a dash panel and front pillar body made from carbon fiber reinforced plastic, and a metal collar joined to the resin member. The collar is a “to-be-fastened part” which is to be fastened to another member by means of fasteners such as a bolt and a nut, as is discussed below.
The to-be-fastened part is coaxial with a mounting hole formed through a front side member of aluminum alloy with a bolt passing through the mounting hole and the to-be-fastened part. The bolt is tightened with a nut to fasten the to-be-fastened part to the front side member so as to attach the front side member to the fastening resin structure.
As for the fastening resin structure disclosed in JP-A-2007-290426, the to-be-fastened part made of metal needs to be joined through an adhesive to the resin member for attachment of the aluminum-alloy-made front side member to the fastening resin structure.
Since carbon fiber reinforced plastic differs from the metal material in coefficient of linear thermal expansion, a change in temperature would generate a stress in the adhesive interposed between the resin member and the to-be-fastened part. Taking this into consideration, it is required that the adhesive maintain a joining strength (to firmly join the to-be-fastened part to the resin member) when a stress is generated in the adhesive due to the temperature change under a high or low temperature environment.
To ensure the maintenance of the joining strength of the adhesive, a joining area between the resin member and the collar may be enlarged. However, the enlargement of the joining area inevitably would make a size of the to-be-fastened part large and hence increase a weight of the fastening resin structure.
The large size of the to-be-fastened part requires a large space for placement of the to-be-fastened part in fastening the fastening resin structure to another structure. This is a hindrance to enhancement of the freedom to design.